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One precursor, three apolipoproteins: The relationship between two crustacean lipoproteins, the large discoidal lipoprotein and the high density lipoprotein/β-glucan binding protein

Stieb, Stefanie, Roth, Ziv, Dal Magro, Christina, Fischer, Sabine, Butz, Eric, Sagi, Amir, Khalaila, Isam, Lieb, Bernhard, Schenk, Sven, Hoeger, Ulrich
BBA - Molecular and Cell Biology of Lipids 2014 v.1841 pp. 1700-1708
Astacus leptodactylus, Macrobrachium rosenbergii, amino acids, apolipoproteins, binding capacity, crayfish, hepatopancreas, high density lipoprotein, lipid transfer proteins, mass spectrometry, open reading frames, peptides, shrimp, transcriptome
The novel discoidal lipoprotein (dLp) recently detected in the crayfish, differs from other crustacean lipoproteins in its large size, apoprotein composition and high lipid binding capacity. We identified the dLp sequence by transcriptome analyses of the hepatopancreas and mass spectrometry. Further de novo assembly of the NGS data followed by BLAST searches using the sequence of the high density lipoprotein/β-glucan binding protein (HDL–BGBP) of Astacus leptodactylus as query revealed a putative precursor molecule with an open reading frame of 14.7kb and a deduced primary structure of 4889 amino acids. The presence of an N-terminal lipid binding domain and a DUF 1943 domain suggests the relationship with the large lipid transfer proteins. Two putative dibasic furin cleavage sites were identified bordering the sequence of the HDL–BGBP. When subjected to mass spectroscopic analyses, tryptic peptides of the large apoprotein of dLp matched the N-terminal part of the precursor, while the peptides obtained for its small apoprotein matched the C-terminal part. Repeating the analysis in the prawn Macrobrachium rosenbergii revealed a similar protein with identical domain architecture suggesting that our findings do not represent an isolated instance.Our results indicate that the above three apolipoproteins (i.e HDL–BGBP and both the large and the small subunit of dLp) are translated as a large precursor. Cleavage at the furin type sites releases two subunits forming a heterodimeric dLP particle, while the remaining part forms an HDL–BGBP whose relationship with other lipoproteins as well as specific functions are yet to be elucidated.